   inf-irreducible element n_i."
   [layout n_i part information]
   (let [upper-neighbours (:upper-neighbours-of-inf-irrs information),
-	inf-irrs (:inf-irrs information),
+	phi_0 (:phi_0 information),
 	positions (first layout),
 
 	pos-n_i (positions n_i),

		   (- (second pos-u_i) (second pos-n_i))]
	edge-rot [(- y_e), x_e],	; rotated edge from n_i to u_i

	phi_n_i (double (phi pos-n_i pos-u_i)),
	phi_0 (double (/ Math/PI (+ 1 (count inf-irrs))))]
    (cond
     (<= 0 phi_n_i phi_0)
     (* (nth edge-rot part)

			    inf-irr-points),

	;; minimize layout energy with above placement as initial value
	[energy, neg-force] (energy-by-inf-irr-positions lattice inf-irrs),
	[new-points, value] (minimize energy
				      ;;neg-force
				      (apply concat inf-irr-points)),

	;; make hash
